Catalyst for the synthesis of ammonia from its elements



Patented Dec. 19, 1922 umrso STATES- 1,439,292 PATENT OFFICE.

JOHN COLLINS CLANCY, OF PROVIDENCE, RHODE ISLAND, 'ASSIGNOR TO THE NITRO- GEN CORPORATION, OF PROVIDENCE, RHODE ISLAND, A CORPORATION OF RHODE I ISLAND.

I CATALYST FOR THE SYNTHESIS OF AMMONIA FROM IT S ELIEiMENTS.

No Drawing. Original application filed January 7, 1920, Serial No. 349,953. Divided and this application filed June 11, 1920.

To all whom it may concern:

. Be it known that I, JOHN COLLINS CLANCY, a subject of the King of Great Britain, residing at Providence, in the county of Providence and State of Rhode Island, have invented certain new and useful Improvements in Catalysts for the Synthesis of Ammonia from Its Elements, of which the following is a specification.

This invention relates to the synthesis of ammonia from its elements through the instrumentality of a catalyst possessing certain novel and particularly valuable properties and characteristics. 5 I v My disclosure herein, also concerns the production of said catalyst; the principal objects of my invention being to reduce the cost of production of the catalytic material, while at the same time increasing its hardiness or durability and thereby increasing its life when in use.

'These and other objects of said inven-p and of materials in the composition of matter which constitutethe catalyst employed in said process, 'will be more especially pointed out in the claims appended hereto;

'As I am aware of various modifications of and changes in my process and preferred catalyst, I desire to be limited only by the scope of said claims, broadly interpreted in the light of my disclosure.

In my application entitle-d: Catalyst for ammonia synthesis and process of preparing the same, Serial No. 346,320, filed December 20, 1919, I described a mode of producing active material from complexcyanogen bearing compounds such as calcium ferrocyanid, barium ferrocyanid, or potassium ferricyanid, etc.

In said application, the desirability of employing a distributive support for the catalytic materialproper, was emphasized; as Was also the mode of .completing the preparation and, finally, the activating of said material after the substance from which it was formed had been completely freed from water. The activation was accomplished by particular heat treatment while the catalyst was surrounded by an atmosphere of mixed hydrogen and nitrogen.

I have now discovered that it is possible.

Serial No. 388,250.

to start with identically the same substance, e. g., calcium ferrocyanid,and by a somewhat analogous and yet essentially differentmode of treatment, produce a catalyst possessing markedly different properties. By way of illustrat on; Starting with a concentrated solution of calcium ferrocyanid in water and sulfur-free and otherwise clean pumice lumps, preferably of about the size ofpeasor a trifle larger,-I immerse the pumice in the solution and evaporate off the water while stirring the mass constantly.

After the charge to be treated has been well dried, preferably at about 100 C., it is then first placed in a preparing autoclave and its temperature is very gradually t1on, both in mode of operation and especially in results.- g i a The operation thus far may be, and, in fact, deslrably is, conducted at atmospheric pressure and the charge under treatment may be conveniently maintained in an atmosphere of mixed hydrogen and nitrogen; I although either hydrogen or nitrogen alone may be'used. Air or freeoxygen is, in any case, excluded; especially as the more ele-v vated temperatures are approached, as even a trace of free oxygen or water is then highly injurious. I

Thus far, the treatment corresponds closely with that which was described, to a like point, in my said co-pending application; but the treatment now to be described differs from what follows in said applica tion, both in mode of ope-ration and especially in results.

The heated material is now subjected to a current of ammonia gas, preferably under atmospheric pressure,to displace the hydrogenpresent in the pores of said material, and the temperature is slowly raised to, say, 400 C., or more; but never desirably above 650 C. In this treatment the need for great care in controlling the temperaapplication; to wit, at about 325 C., and it is capable of synthesizing ammonia from its elements even at this low temperature.

Said catalyst may moreover, be improved and the catalyst is not injured thereby. Here catalyst (or class of catalysts) described my said application, is hlghly pyrophonc.

after activation, even when at room temperature.

The present non-'pyrophorlc catalyst, prepared as aforesaid, may now be cooled and transferred to the working or synthesizing autoclave, with exclusion of air; but I prefer to eject it, while hot, directly from the preparingautoclave into the working auto- 'clave, by a jet of-the synthesizing gases,

air being, of course, carefully excluded during this transference.

The herein described treatment of the catalytic material, permits-of elevating the temperatureof the catalyst, under synthesizing conditions, to 500 C. or even to 600 (1;

again, it distinguishes from my earlier catalyst, which if heated to, say, 550 C.,-and especially if heated,,above 600 C.,-under synthesizing conditions, becomes very seri ously impaired, or it may be ruined, if said temperature be maintained forbut a few hours.

The present catalytic bodies are more easily controlled; there being practically never any tendency for their temperatures to inadvertently run up, if merely reasonable care be exercised in the control of the exothermic synthesizing reaction. They can be handled with less care, being far less delicate. They actively synthesize ammonia at lower temperatures; the preferred temperature in the present case being about 400 (1, or somewhat less, rather than 450 0.; which, of course, prolongs the life of the autoclave. The preferred operating pressure is about one hundred atmospheres.

formed in part, has been dried at tempera tures ranging gradually up from 100 C. to 150 C.,-may then be subjected to theaction of ammonia gas for but a few hours, at.

from 400 to 450 C. and thereupon be at once ready for the synthesizing operation.

The initial precentage yield from these catalysts, if both are operated at, say, 450 C. under the same conditions, is about the same; but the yield of the earlier catalyst falls off more rapidly, and it requires occasional periods of rest; whereas the present ammoma-gas-treatedcatalyst does not thus tend to. become fatigued, and its yield holds up for a. much longer time. Toward the end of its life, the yield gradually falls,

while with the earlier catalyst, there is usually an abrupt drop in yie d as the end of its period of commercial usefulness is approached.

Also, the space-timeyield of the new catalyst, herein described, is much greater; as the rate of flow of gases thereover can be greatly increased without injury to the catalyst.

Again, the earlier catalyst requires a distributive support such as pumice lumps; since, otherwise, it is too concentrated and being very sensitive, becomes over-heated unless the proper control of the temperature, favored by the support,'is eXercisecL' In the present catalyst, while the pumice support or the like is desirable, to aflord porosity and to economize catalytic material, said support is by no means essential, as no exothermic reaction'is involved in its'preparation.

The exact composition of the replacement compounds formed by thus reacting with ammonia gas upon cyanogen compounds, or mixturesof compounds or substances oneat least of which has initially a high cyanogen content,is exceedingly difiicult to determine, and I am of the opinion that it is quite complex; being possibly in the nature of a complex salt including the groups (ON) or (CN,), and (NH or (NH). At any rate, there appears to be present therein after the finished product has been formed, not only 7 nitrogen directly united to carbon by a plurality of bonds; but also, nitrogen free from direct connection with carbon.

not too high; and when free cyanogen, o1"

HCN, is no longer liberated at a given op-' erating pressure the use. I y V By way of further illustratio1 1, it will be well to state that whenthus producing an addition compound by means of ammonia, I

catalyst is ready for previously mentioned, but, also, with such double salts as: Y i

K Cr CN),; K Cr(CN),; CoCaFeCN K,Mn( N) Ba Mn(CN),; K,Mn ON etc.

Preferably, for convenience and cheapness of preparation of the catalyst, I start with such compounds, or mixtures of sub.

stances as the foregoing; because of their solubility in water; although insoluble com-- pounds such as: V

K Ce(CN),; Sr Ti(C'N)- and the like may be used.

These latter, however, do not permit of the ready formation therefrom, of films of catalytic material on pumice or the, like, and

I they are, too, more costly.

The ammonia gas used in their treatment is preferably pure; but it may be diluted with non-harmful gas, such as the gaseous mixture of nitrogen and hydrogen used in the synthesizing operation; care being taken, in this case, to avoid such an excessive dilution of the'ammonia as would impair its action upon the material under treatment. In general, the more concentrated the ammonia, the better.

The term alkalinous metal as used in certain of the appended claims is intended to refer to such metals as: calcium, strontium, barium, potassium, etc.; this expression being employed to avoid circumlocution in said claims.

Some of these metals are more adapted to the production'of an 'eflicient catalyst than others; the catalytically active metal potassium, for example, being superior to sodium, and calcium being, likewise, greatly to be preferred to magnesium. I have particularly specified the preferred metals of this type, because such specified metals are both very well adapted to the purpose in question, and because, also, they are not rare or costly. Obviously this latter factor mustbe taken into consideration if the synthetic operation is to be of real value.

For analogous reasons, and because of the solubility of their cyanids, the auxiliary or less basic metal or metals, present in the complex catalyst, should desirably be either chromium, iron or manganese.

and are, hence, more difiicult to deposit to advantage upon the carrier preferably employed.

This case is a division of my pending application, Serial #349,953, filed January 7, 1920; entitled: Synthesis of ammonia from its elements.

-Having, thus described my invention, what I claim is:

1. The process of preparing a catalyst Titanium, for example, is also well suited for use in may start with not only the 1ron-.cyan1 d s adapted for the synthesis of ammonia from its elements, which comprises coating the walls of a porous support for the active maport with a solution of a double cyanid which is soluble in water, evaporating ofi saidwater, andreacting upon thesolid residues with heat and ammonia gas.

2. The process of preparing a catalyst adapted for the synthesis of. ammonia from its elements, which comprises replacin a. part only of the cyanogen content 0% a quantity of cyanogen bearing material, with nitrogen directly united to hydrogen.

3. he process of preparing a catalyst adapted for the synthesis of ammonia from its elements, which comprises reacting with ammonia upon a mass of material which has a high cyanogen content and which also includes an alkalinous metal,to replacev a part only of the cyanogen, present in said mass, with nitrogen directly united to hydrogen.

4. The process of preparing a catalyst adapted for the synthesis of ammonia from' its elements, which comprises reacting with ammonia upon material which includes nitrogen united to carbon by a plurality of bonds and which also includes an alkalinous trogen united to carbon by a plurality of bonds and which also includes an alkalinous metal and a second and materially less basic metal to replace a part of said nitrogen in said mass by nitrogen which is free from direct connection with carbon.

6(The process of preparing a catalyst adapted for the synthesis of ammonia from its elements, which comprises the heating of an alkalinous metal cyanid in an atmosphere from which oxygen is excluded, and subsequently subjecting the same to contact with ammoma gas at an elevated temperature.

7. The process of preparing a catalyst adapted for the synthesis of ammonia from its elements, which comprises the heating of the catalytic material in the presence of ammonia to activate the same. 1 0 8. A catalyst adapted for the synthesis of ammonia from its elements, which comprises a catalytically active, substantially non-pyrophoric. product resulting from the treatment of a double cyanid with hot am- 12 monia gas. Y 9. A catalyst adapted for the synthesis of ammonia from its elements, which come prises a catalytically active, substantially non-pyrophoric product resulting from the treatment of a double cyanid with hot ammonia gas, one of the metals in the base of said cyanid being alkalinous in character.

10. A catal st adapted for the synthesis of ammonia rom its elements, which comprises a catalytically active, substantially non-pyrophoric product resulting from the treatment'of a double cyanid with hot am.- monia gas, one of the metals in' the base of said cyanid being alkalinous in character and another of said metals being materially less basic than said alkalinous metal.

11. A catalyst adapted for the synthesis of ammonia from its elements, which comprises a porous support the walls of the pores of which are coated with films of cyanogen bearing material deposited from solution upon said walls and there reacted upon with ammonia gas to render said films catalytically active.

12. A catalyst adapted for the synthesis of ammonia from its elements, which comprises a porous support the walls of the pores of which are coated with films of cyanogen bearing material deposited from I 1 ,asesea catalytically active, said films including an alkalinous metal and a less basic co-acting unetal-intimatialy associated therewith. a

13. A catalyst adapted for the synthesis of ammonia from its elements which comprises a catalytically active product resulting from the treatment of a cyanogen salt of a base forming element with ammonia gas under the influence of heat.

14; A catalyst adapted for the synthesis of ammonia from its elements which comprises a catalytically active product resulting from the heating of a cyanogensalt of a base formingelement in the presence of ammonia gas and under super-atmospheric pressure.

In testimony whereof I have afiixed my signature, in the presence of two witnesses.

JOHN COLLINS CLANCY.

Witnesses:

MILDRED H. ANDREWS, HELEN M. BARNBRooK. 

